1. Field of the Invention
The present invention relates to an apparatus and method for driving a motor whose characteristics are not known and more particularly to the driving of a transformer commutated brushless DC motor and especially one used for very large data storage in a rotary tape recorder.
2. Description of the Prior Art
When working with tape recorders for purposes of storing large amounts of data, a very accurate and constant drive motor is required. One form of such a motor is a transformer commutated brushless DC motor such as is sold by Panasonic in the AG-6300 Video Cassette Recorder. The Panasonic Video Cassette Recorder is accompanied by its own custom made integrated circuits to drive the scanner motor and since these integrated circuits are not readily available when the apparatus is modified for use in a very large data storage apparatus it is necessary that a driving circuit capable of starting and driving the motor be created with use of standard and inexpensive parts. Unfortunately without knowing the characteristics of the motor a problem arises in being able to start the motor since the magnetic nature of the motor is such that it may stall because of the placement of the magnetic poles with respect to the transformer windings. Also to run the motor reliably it is necessary to know the magnitude of the signals which are created by the position sensing coils, since without this knowledge control of the motor is difficult and sometimes impossible.